Performance of Gasoline Compression Ignition (GCI) with On-Demand Reactivity Enhancement over Simulated Drive Cycles 2018-01-0255
Gasoline compression ignition (GCI) combustion is a promising solution to address increasingly stringent efficiency and emissions regulations imposed on the internal combustion engine. However, the high resistance to auto-ignition of modern market gasoline makes low load compression ignition (CI) operation difficult. Accordingly, a method that enables the variation of the fuel reactivity on demand is an ideal solution to address low load stability issues. Metal engine experiments conducted on a single cylinder medium-duty research engine allowed for the investigation of this strategy. The fuels used for this study were 87 octane gasoline (primary fuel stream) and diesel fuel (reactivity enhancer). Initial tests demonstrated load extension down to idle conditions with only 20% diesel by mass, which reduced to 0% at loads above 3 bar IMEPg. Engine performance over a mode weighted drive cycle was completed based on work by the Ad-Hoc fuels committee  to demonstrate the performance of various levels of fuel blending for five primary modes of operation encompassing low load to high load. Lastly, several simulated transient drive cycle were analyzed to investigate the consumption rate of the reactivity enhancer. A response model was fit to the experimental data and exercised over the load based drive cycle. Results showed that the diesel consumption could be reduced to additive levels over a 10 k mile oil change interval, lower than diesel exhaust fluid (DEF), which presents a pathway to a full-time GCI engine.